Patent GB-325214-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M5/08
Filed: 1928-11-12
Abstract: 325,214. Standard Telephones & Cables, Ltd., (Western Electric Co., Inc.). Nov. 12, 1928. Manual exchange party-line systems. - A junction when taken into use by the A operator is automatically connected by an individual relay to the B operator's set and to a set of keys by which she selects the ringing current to be applied to a party line or, when the call is to be extended to another operator, prevents ringing. The operation of any one of these keys also serves to disconnect the junction from the position circuit, but the B operator may reconnect by means of a key controlling the individual relay. Call to a party-line subscriber. When the A operator plugs into the jack 3 of the junction T2, line relay 4 energizes, lighting lamp 5 and operating start relay 13 through the medium of relay 12. Relay 27 energizes in series with relay 33, which locks and connects up sluggish relay 34. Relay 13 opens the energizing circuit for relays corresponding to 27 associated with the junctions having a number higher than T2, while relay 27 opens the energizing circuit for relays corresponding to 13 associated with the junctions having a number lower than T2. When the B operator's set OT is plugged into jacks 45, 46, relays 47, 48, 49, 44 are operated, and relay 40 now energizes, flashing lamp 5 by periodically shortcircuiting it under control of interrupter 55. Relay 57 energizes over 58, 60, 62, 63, 64, 65, 66, 68, 70, connecting the junction to the position circuit and connecting relays 18, 75 to the ringing key equipment. Relay 79 energizes in series with marginal relay 20 which does not operate at this time, and relay 80 energizes over the upper winding of relay 57, this circuit serving to hold the latter relay while relay 20 is inoperative. Relay 71 pulls up and locks, disconnecting battery from the emergency keys such as 99 to prevent the operation thereover of the relay corresponding to 57 associated with any other junction, and effecting the operation in turn of relays 108, 113, 114, 115, 101 to send back two impulses of tone current from transformer 118 to signal the A operator that she may communicate the wanted number to the B operator. Before plugging into the wanted line, the B operator presses the ring- ing key appropriate to the subscriber required to select the ringing current to be sent, viz. positive or negative pulsating current on one or other conductor. Assuming this key to be M, relays 134, 85 energize and lock, closing circuits for opera.ting relays 18, 75, which lock under control of ring cut-off relay 16. Relay 143 also pulls up, and closes a circuit through the lower winding of marginal relay 20, which now energizes and locks over its upper winding, effecting release of relays 13, 27, 57, so that the junction is disconnected from the position circuit, and lamp 5 lights steadily. When the operator plugs into the wanted line, sleeve relay 8 energizes, extinguishing lamp 5, and ringing relay 151 energizes over interrupter 154 and locks, connecting positive pulsating ringing current to the tip side and ground to the ring side of the called line. The operation for keys J, R, W is similar except that for J, relay 75 does not operate, for R, relay 18 does not operate, and for W, neither of these relays operates. On reply, ring cut-off relay 16 energizes and releases relays 20, 18, 175, 151, while relay 165 energizes over the loop, and connects up reversing relay 166 to give supervision to the A operator. When the A operator disconnects, relays 4, 12 fall back, and relay 10 energizes to light lamp 5 to give a disconnect signal. Should the junction be seized again before the B operator has cleared, relay 10 prevents any effective operation of the ringing keys. Trunk or other call in which ringing is suppressed. Key TK is operated and relays 146, 18 energize, the latter releasing relays 13, 27, 40 and stopping the flashing of lamp 5. Relay 57 is released through the medium of relays 143, 172, 87, 80 to dimsconnect the junction from the position circuit, but marginal relay 20 is not energized, so that ring- ing relay 151 cannot operate when the operator plugs into an outgoing junction. The connection may be extended in this way to obtain information from a special operator. The B operator then presses emergency key 99 while withdrawing the plug, so that sleeve relay 8 releases and relay 57 energizes over relay 95 in the position circuit and locks as before in series with relay 80. Relay 95 connects up relay 181 to short-circuit relay 18. The connection to the wanted subscriber is then set up as already described. Emergency working. If the sequence relays such as 13, 27 are not operating properly, emergency key 99 may be used to connect the junction to the operator's set by the energization of relay 57. Relay 71 energizes as before to prevent double connections, but the locking of this relay may be prevented by the operation of key 175, which also disables tone relays 108, 113, 114, 115, 101.